This invention relates to a linear/rotary actuator and a winding machine including the same, and more particularly to a linear/rotary actuator suitable for driving a machine or equipment carrying out both linear motion and rotary motion such as an arm of a robot or a nozzle of a winding machine and a winding machine including the same.
Driving of, for example, an arm of a robot, a nozzle of a winding machine or the like often requires an actuator constructed so as to carry out linear motion and rotary motion not only individually (linear/rotary uniaxial motion) but concurrently (linear/rotary biaxial motion). Actuators for such biaxial motion include two type of actuators. One of them is a linear/rotary actuator of the type that simply an actuator for linear motion and that for rotary motion are combined with each other and more particularly a rotary driving motor and a linear driving motor are independently arranged so as to transmit power through a complicated transmission mechanism to a single output shaft to carry out rotary/linear biaxial motion. The other actuator is a linear/rotary actuator of the type that a rotary driving motor and a linear driving motor are linearly arranged to directly carry out rotary driving of an output shaft or linear driving thereof without using any complicated transmission mechanism. The actuator of the latter type is disclosed in, for example, in Japanese Patent Application Laid-Open Publication No. 296308/1993, wherein two motors linearly arranged in juxtaposition to each other so as to define an axis of the actuator by cooperation with each other permit a single output shaft to carry out linear/rotary biaxial motion. Both former and latter linear/rotary actuators are disclosed in Japanese Patent Application Laid-Open Publication No. 292343/1994.
The linear/rotary actuator disclosed in Japanese Patent Application Laid-Open Publication No. 292343/1994 is so constructed that a single output shaft is formed with both a ball screw and a spline. The ball screw and spline are driven either through a transmission mechanism or directly by means of both a rotary driving motor and a linear driving motor. Unfortunately, such construction of the linear/rotary actuator disclosed causes a problem that the output shaft carries out linear motion with rotation of a rotor of the rotary driving motor when a rotor of the linear driving motor is kept interrupted during rotary motion. In order to solve the problem, it is required to control the linear driving motor in coordination with the rotary driving motor during rotation thereof. This renders control of both motors highly troublesome and complicated and leads to both a failure in control and misregistration in control.
Also, the above-described latter linear/rotary actuator disclosed in Japanese Patent Application Laid-Open Publication No. 296308 is so constructed that the single output shaft described above is adapted to carry out both rotary motion and linear motion and formed with a ball screw and a spline. The ball screw is threadedly engaged with a nut driven for rotation through the linear driving motor and the spline is linearly movably fitted in a groove of a shaft driven for rotation through the rotary driving motor. Driving of the linear driving motor rotates the nut, leading to linear motion of the output shaft, whereas driving of the rotary driving motor leads to rotation of the output shaft through the shaft. Such construction of the linear/rotary actuator permits it to be relatively simplified in structure and reduced in whole size. However, the linear/rotary actuator causes linear motion and rotary motion to be mechanically synchronized with each other, to thereby fail to individually carry out linear motion and rotary motion. For example, it fails in execution of only rotary motion, because the ball screw is rotated relatively to the nut, to thereby fail to rotate the output shaft while holding it against linear motion. Likewise, it fails to concurrently carry out both linear motion and rotary motion because it ensures linear motion in only one direction but causes a reduction in speed of linear motion in the other direction or fails in linear motion in the other direction. Such a restriction fails to permit the linear/rotary actuator to satisfactorily exhibit general-purpose properties.
Also, the conventional linear/rotary actuator fails to optionally and positively carry out linear motion and rotary motion, leading to a failure to permit so-called box motion (linear motion, rotation, linear motion and rotation) as required in operation of a nozzle of a winding machine to be repeatedly executed at an increased speed.